Mobile phone

ABSTRACT

The mobile phone includes an optical sensor, a display element, a pixel circuit portion where a plurality of pixels having a plurality of transistors are arranged in matrix, an optical sensor control circuit which is connected to an optical sensor driver circuit for driving the optical sensor and reads a signal from the optical sensor, a display portion control circuit which is connected to a display element driver circuit for driving the display element and outputs an image signal for displaying an image on a display portion, a gradient detection portion for outputting a signal in accordance with a gradient of the mobile phone, and an arithmetic circuit for performing display in the pixel circuit portion by switching image signals output to the display portion control circuit with a signal from the gradient detection portion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile information-communicationdevice, or a mobile phone. In particular, the present invention relatesto a mobile information-communication device which includes a displayportion where an optical sensor is provided in each pixel, or a mobilephone which includes a display portion where an optical sensor isprovided in each pixel.

2. Description of the Related Art

As mobile phones have higher performance, the convenience thereof hasbeen improved. Higher definition of display portions, higher capacity ofcommunication functions, smaller electronic components, and the likegreatly affect higher performance of mobile phones and help the spreadof mobile phones. In particular, higher performance of display portionshas recently developed actively and has contributed to improvement inconvenience for users.

Reference 1 (Japanese Published Patent Application No. 2002-33823)discloses the structure of a mobile phone which is a mobileinformation-communication device, where optical sensors are provided ina plurality of pixels of a display portion and an authentication systemfor reading individual information related to users to performauthentication is provided, as one proposal for higher performance ofdisplay portions.

As for mobile phones, multifunctional models having an image function ofreceiving television broadcasts to display images, a calling functionusing communication through base stations of mobile phones, and afunction of transmitting and receiving e-mail or the like through theInternet, have developed and have widely spread. On the other hand, inactual conditions, switching of functions of mobile phones is performedby touching operation buttons provided for the mobile phones by theusers of the mobile phones or reading of external light by opticalsensors provided in a display portion. However, the switching offunctions of mobile phones by touching operation buttons or a displayportion in which optical sensors are provided by users in each casemakes operations complicated and hampers convenience.

Further, depending on functions of mobile phones to be used andoperating methods of the mobile phones, by optimizing the size orarrangement of operation buttons and a display portion in which opticalsensors are provided, operability can be improved. However, theoperation buttons are mounted on the mobile phones, so that the size orarrangement cannot be optimized. Furthermore, in a touch-panel typedisplay portion in which optical sensors are provided, operations by theusers are needed to switch the arrangement of input keys which aredisplayed on the display portion, so that convenience is hampered.

SUMMARY OF THE INVENTION

In view of the foregoing problems, the present invention provides amobile phone which can be used without hampering convinience in acondition where functions of the mobile phone are switched. The presentinvention provides a mobile phone which optimizes the size orarrangement of input keys which are displayed on a display portion inwhich optical sensors are provided depending on functions of a mobilephone to be used and an operating method of the mobile phone, so thatoperability can be improved.

In accordance with one aspect of the present invention, the followingobjects are included: an optical sensor, a display element, a pixelcircuit portion where a plurality of pixels having a plurality oftransistors are arranged in matrix, an optical sensor control circuitwhich is connected to an optical sensor driver circuit for driving theoptical sensor and reads a signal from the optical sensor, a displayportion control circuit which is connected to a display element drivercircuit for driving the display element and outputs an image signal fordisplaying an image on a display portion, a gradient detection portionfor outputting a signal in accordance with the gradient of a mobilephone, and an arithmetic circuit for performing display in the pixelcircuit portion by switching image signals output to the display portioncontrol circuit with a signal from the gradient detection portion.

In addition, in accordance with another aspect of the present invention,the following objects are included: an optical sensor, a displayelement, a pixel circuit portion where a plurality of pixels having aplurality of transistors are arranged in matrix, an optical sensorcontrol circuit which is connected to an optical sensor driver circuitfor driving the optical sensor and reads a signal from the opticalsensor, a display portion control circuit which is connected to adisplay element driver circuit for driving the display element andoutputs an image signal for displaying an image on a display portion, agradient detection portion for detecting whether the gradient of amobile phone is longitudinal or lateral and outputting a signal inaccordance with the gradient, and an arithmetic circuit for performingdisplay in the pixel circuit portion by switching an image signal outputto the display portion control circuit with the signal in accordancewith the gradient.

Further, in accordance with another aspect of the present invention, thefollowing objects are included: an optical sensor, a display element, apixel circuit portion where a plurality of pixels having a plurality oftransistors are arranged in matrix, an optical sensor control circuitwhich is connected to an optical sensor driver circuit for driving theoptical sensor and reads a signal from the optical sensor, a displayportion control circuit which is connected to a display element drivercircuit for driving the display element and outputs an image signal fordisplaying an image on a display portion, a gradient detection portionfor detecting whether the gradient of a mobile phone is in a firststate, a second state, or a third state and outputting a signal inaccordance with the gradient, and an arithmetic circuit for performingdisplay in the pixel circuit portion by switching an image signal outputto the display portion control circuit with the signal in accordancewith the gradient.

According to the present invention, a mobile phone which can be usedwithout hampering convinience in a condition where functions of themobile phone are switched can be provided. Further, a mobile phone whichoptimizes the size or arrangement of input keys which are displayed on adisplay portion in which optical sensors are provided depending onfunctions of a mobile phone to be used and an operating method of themobile phone, so that operability can be improved, can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a block diagram for illustrating Embodiment Mode 1;

FIGS. 2A to 2D are diagrams for illustrating Embodiment Mode 1;

FIGS. 3A to 3D are diagrams for illustrating Embodiment Mode 1;

FIGS. 4A to 4D are diagrams for illustrating Embodiment Mode 1;

FIGS. 5A to 5C are diagrams for illustrating Embodiment Mode 1;

FIGS. 6A to 6C are diagrams for illustrating Embodiment Mode 1;

FIGS. 7A and 7B are diagrams for illustrating Embodiment Mode 1;

FIG. 8 is a block diagram for illustrating Embodiment Mode 2;

FIGS. 9A and 9B are circuit diagrams for illustrating Embodiment Mode 2;

FIGS. 10A to 10D are cross-sectional views for illustrating EmbodimentMode 3;

FIGS. 11A to 11F are cross-sectional views for illustrating EmbodimentMode 3;

FIGS. 12A to 12C are cross-sectional views for illustrating EmbodimentMode 3;

FIGS. 13A and 13B are cross-sectional views for illustrating EmbodimentMode 3;

FIG. 14 is a top view for illustrating Embodiment Mode 3;

FIG. 15 is a cross-sectional view for illustrating Embodiment Mode 4;

FIG. 16 is a cross-sectional view for illustrating Embodiment Mode 4;

FIG. 17 is a cross-sectional view for illustrating Embodiment Mode 4;

FIG. 18 is a cross-sectional view for illustrating Embodiment Mode 4;and

FIG. 19 is a perspective view for illustrating Embodiment Mode 5.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiment modes of the present invention will be describedwith reference to the drawings. Note that the present invention can beimplemented in various different ways and it will be readily appreciatedby those skilled in the art that various changes and modifications arepossible without departing from the spirit and the scope of the presentinvention. Therefore, the present invention should not be construed asbeing limited to the following description of the embodiment modes. Notethat in all the drawings for describing the embodiment modes, likeportions or portions having similar functions are denoted by the samereference numerals, and description thereof is not repeated.

Embodiment Mode 1

In this embodiment mode, the structures and functions of a mobile phoneare described with reference to a block diagram and the like. Note thata mobile phone in this specification refers to a mobileinformation-communication device which has an image function of, forexample, receiving television broadcasts to display images, a callingfunction using communication through base stations of the mobile phone,a function of transmitting and receiving e-mail or the like through theInternet, or the like. Note that the number of functions of a mobilephone may be plural, and the functions are not limited to the abovefunctions.

FIG. 1 is a block diagram of a mobile phone which is described in thisembodiment mode. The mobile phone shown in FIG. 1 includes a pixelcircuit portion 101, a display element driver circuit 102, an opticalsensor driver circuit 103, a display portion control circuit 104, anoptical sensor control circuit 105, a gradient detection portion 106, anarithmetic circuit 107, a signal transmission/reception portion 108, anexternal input/output portion 109, and a memory portion 113.

In FIG. 1, a plurality of pixels 110 are provided in the pixel circuitportion 101, and a display element 111 and an optical sensor 112 areprovided in each of the plurality of pixels. The display element drivercircuit 102 includes a data line driver circuit and a scan line drivercircuit (both are not shown) and controls the display elements 111 inthe pixel circuit portion 101. The optical sensor driver circuit 103includes an optical sensor signal line driver circuit and an opticalsensor scan line driver circuit (both are not shown), controls theoptical sensors 112 in the pixel circuit, and detects signals from theoptical sensors 112. The display portion control circuit 104 outputsimage data or the like for performing display on the pixel circuitportion 101 to the display element driver circuit 102, based on signalsfrom the arithmetic circuit 107. The optical sensor control circuit 105outputs signals or the like for detecting external light by the opticalsensors 112 provided in the pixel circuit portion 101 to the opticalsensor driver circuit 103, based on signals from the arithmetic circuit107, and encodes signals from the optical sensors 112, which areobtained in the optical sensor driver circuit 103, to output thesesignals to the arithmetic circuit 107. The gradient detection portion106 detects the gradient of the mobile phone and outputs signals inaccordance with the gradient of the mobile phone to the arithmeticcircuit 107. The arithmetic circuit 107 writes or reads signals to orfrom the memory portion 113 based on signals from the gradient detectionportion 106, and converts signals from the signal transmission/receptionportion 108, the external input/output portion 109, and the opticalsensor control circuit 105 in accordance with functions desired by auser to output these signals to the display portion control circuit 104,the signal transmission/reception portion 108, and the externalinput/output portion 109.

The signal transmission/reception portion 108 includes an antenna 114and a transmission/reception circuit 115. The antenna 114 receives andtransmits radio signals from and to the outside. Note that the antenna114 may have a function of receiving radio signals related to movingimages of television broadcasts or the like. The transmission/receptioncircuit 115 has a function of demodulating data signals of radio signalsreceived by the antenna 114, a function of modulating data signals ofradio signals transmitted from the antenna 114, and the like.

The external input/output portion 109 includes a speaker 116, amicrophone 117, a sound processing circuit 118, an operation key 119,and an interface 120. The speaker 116 outputs sound based on datasignals related to sound superimposed over the radio signals. Themicrophone 117 converts the sound of the user of the mobile phone intosignals. The sound processing circuit 118 generates analog signals whichare output to the speaker 116 and encodes signals based on the soundconverted by the microphone 117, for example. In addition, the operationkey 119 is operated by the user and converts the operation into electricsignals and outputs the electric signals. Further, the interface 120inputs and outputs signals between the sound processing circuit 118 andthe operation key 119, and the arithmetic circuit 107.

In the memory portion 113, a program for processing signals output tothe display portion control circuit 104 in the arithmetic circuit 107based on signals from the gradient detection portion 106 and a programrelated to processing of signals which are input and output to and fromthe signal transmission/reception portion 108 and the externalinput/output portion 109 are stored. For example, the memory portion 113includes a ROM (read only memory) 121 and a RAM (random access memory)122.

Note that the above structures of the signal transmission/receptionportion 108, the external input/output portion 109, and the memoryportion 113 are shown as examples, and the present invention is notlimited to the above structures.

Note that by forming the gradient detection portion 106 by using, forexample, a gyroscope or a triaxial acceleration sensor, a desiredfunction can be obtained. As a gyroscope, a mechanical gyroscope, aliquid gyroscope, or an optical gyroscope may be used.

Note that as the gradient detection portion 106 in the presentinvention, a smaller component for detecting gradients is preferablyused particularly. In such a case, it is preferable to use a triaxialacceleration sensor using a MEMS technology because reduction in size ofthe mobile phone can also be achieved.

Note that although a structure where a gradient detection portion isprovided is shown as the structure of the mobile phone of the presentinvention, a structure where a different sensor is provided may be used.As a sensor other than a sensor which detects gradients, a sensor whichdetects positions, magnetism, temperature, chemical substances, sound,radiations, or the like can be given. By including a plurality ofsensors, a more multifunctional mobile phone can be provided. Forexample, in the case where a position sensor detects the fact that themobile phone is in an area (an area around priority seats on a train)where a calling function is prohibited, a function of limiting part ofthe functions (the calling function) in accordance with the gradient ofthe mobile phone can be realized.

Next, the operations of the gradient detection portion 106 and thearithmetic circuit 107 with the structures described in FIG. 1 aredescribed with reference to the appearance (perspective views andschematic views) of the mobile phone in FIGS. 2A to 2D, FIGS. 3A to 3D,FIGS. 4A to 4D, FIGS. 5A to 5C, FIGS. 6A to 6C, and FIGS. 7A and 7B.Note that the shape of the display portion of the mobile phone isdescribed as a rectangular shape which has long sides and short sides inthe case where a display surface is seen from the front. Note thatalthough the shape of a housing in which the display portion of themobile phone is stored is not limited to a rectangular shape in the casewhere the display surface is seen from the front, the shape of thehousing is preferably a rectangular shape from the viewpoints ofoperability and reduction in size. Note that the corners of the housingof the mobile phone may have rounded shapes or chamfered shapes from theviewpoints of safety and durability.

FIG. 2A is a perspective view of a mobile phone. The mobile phone shownin FIG. 2A is described assuming that a user utilizes a calling functionusing communication through base stations of the mobile phone when theuser uses the mobile phone. In the perspective view shown in FIG. 2A, amobile phone 200 includes a display portion 201, an operation key 202, aspeaker 203, a microphone 204, and an imaging lens 205. Note that aplurality of pixels are provided in the display portion 201 and adisplay element and an optical sensor are provided in each of theplurality of pixels, as described in FIG. 1.

Note that in this specification, an operation key refers to an objectwhose movable portion such as a push button is moved so that electriccontrol is performed.

In addition, FIG. 2B is a perspective view of the mobile phone with astructure which is different from that of FIG. 2A. FIG. 2B differs fromFIG. 2A in that the speaker 203 and the microphone 204 are provideddiagonally in a rectangle in the case where a display surface is seenfrom the front. By providing the speaker 203 and the microphone 204diagonally in the mobile phone, the speaker 203 and the microphone 204can be provided so as to be separate from each other. Therefore, aproblem in that a calling function is decreased because the speaker 203or the microphone 204 is apart from the ear and mouth when the mobilephone is made smaller is solved, so that convenience in utilizing thecalling function of the mobile phone can be improved.

In the case where the calling function of the mobile phone is utilized,the following functions are used in sequence by the user: 1) a functionof selecting and specifying an intended party with an input key, 2) afunction of inputting the telephone number of the intended party withthe input key, and 3) a function of reading the user from notificationfrom the intended party. The above functions 1) to 3) are used when themobile phone is used by the user with the housing of the mobile phoneset in a longitudinal direction, that is, with a gradient where along-side direction of a rectangle is a perpendicular direction in thecase where the display surface is seen from the front. When thefunctions are described with reference to a schematic view of a displaysurface of a mobile phone shown in FIG. 2C, display 251 of the intendedparty and the telephone number and display 252 of numbers and an inputkey for selection are provided in the display portion 201. The user whouses the calling function of the mobile phone selects the intended partyand the telephone number through the display of the input key inaccordance with the above functions 1) to 3) and talks on the phone.

Note that in this specification, the case where a mobile phone is in alongitudinal direction refers to the case where a mobile phone has agradient where a long-side direction of a rectangle is a perpendiculardirection in the case where a display surface is seen from the front.Further, the case where a mobile phone is in a lateral direction refersto the case where a mobile phone has a gradient where a long-sidedirection of a rectangle is a horizontal direction in the case where adisplay surface is seen from the front.

Note that in this specification, an input key refers to a region foroperation, which is displayed on a display portion provided with anoptical sensor. That is, the size or arrangement of an input key can bevaried in accordance with display on the display portion.

In the present invention, a gradient detection portion is providedinside the mobile phone; signals which are output from the arithmeticcircuit to the display portion control circuit are switched by signalsin accordance with the degree of the gradient of the mobile phone in thegradient detection portion; and display is performed on the displayportion in which the pixel circuit portion is provided. That is, in thegradient detection portion, when the mobile phone detects the fact thatthe housing is in a longitudinal direction as shown in FIG. 2A, thearithmetic circuit performs processing so that display with the displayelement provided in each pixel is performed as shown in FIG. 2C and thekind, size, or arrangement of the input key can be varied by the opticalsensor provided in each pixel. Therefore, the display region of theinput key can be minimized in accordance with a function used by theuser, so that the size and arrangement of the input key can beoptimized.

Note that in the schematic view in the case where the calling functionof the mobile phone shown in FIG. 2C is utilized, the display 251 of theintended party and the telephone number and the display 252 of thenumbers and the input key for selection are shown in the display portion201. The schematic view in the case where the calling function of themobile phone shown in FIG. 2C is utilized can be described by dividingthe display portion of the mobile phone into a segment display region211, an image display region 212, and an input key display region 213,as shown in FIG. 2D. The present invention is not limited to the abovedisplay region; however, by using a structure where a display elementand an optical sensor are provided in each pixel and a structure where agradient detection portion is provided, the display region can beoptimized depending on functions in accordance with usability for theuser. Note that although the example in which the segment display region211 is displayed taking usability of the mobile phone into considerationis shown in FIG. 2C and FIG. 2D, the calling function can be usedwithout particularly displaying the segment display region 211.

Note that although the structure where the mobile phone 200 includes theimaging lens 205 is shown in FIG. 2A, a structure where the mobile phone200 does not include the imaging lens 205 may be used. Note that wheninformation related to the gradient of the mobile phone is obtained byperforming image processing of an image taken by a camera function ofthe mobile phone 200, in addition to the signals in accordance with thedegree of the gradient of the mobile phone in the gradient detectionportion, a function of converting the functions of the mobile phone withfewer malfunctions can be realized, which is preferable.

In FIG. 2A, an example of a function in the case where the mobile phoneis used in a longitudinal direction by the user is shown assuming thatthe calling function of the mobile phone is utilized. In each of FIGS.3A to 3D, FIGS. 4A to 4D, FIGS. 5A to 5C, FIGS. 6A to 6C, and FIGS. 7Aand 7B, an example of a function in the case where the mobile phone isutilized by the user with a gradient where a short-side direction of arectangle is a longitudinal direction in the case where the displaysurface is seen from the front, that is, in a lateral direction and witha long-side direction fixed and a short-side direction inclined, isdescribed.

First, in FIGS. 3A to 3D, a schematic diagram and perspective views ofthe mobile phone when the mobile phone is utilized with a gradient wherea short-side direction of a rectangle is a longitudinal direction in thecase where the display surface is seen from the front and with along-side direction fixed and a short-side direction inclined, aredescribed. FIG. 3A shows examples of gradients of the short-sidedirection of the rectangle in the case where the display surface of themobile phone is seen from the front. FIG. 3A shows switching offunctions of the mobile phone when the short-side direction of therectangle is a substantially perpendicular direction (also referred toas a perpendicular direction), an oblique direction, or a substantiallyhorizontal direction (also referred to as a horizontal direction) in thecase where the display surface of the mobile phone is seen from thefront. That is, switching of the functions of the mobile phone when themobile phone is in a lateral direction is described.

FIG. 3B is a perspective view of the mobile phone when the short side ofthe rectangle is a substantially perpendicular direction in the casewhere the mobile phone shown in FIG. 3A is seen from the front. FIG. 3Cis a perspective view of the mobile phone when the short-side directionof the rectangle is an oblique direction in the case where the mobilephone shown in FIG. 3A is seen from the front. FIG. 3D is a perspectiveview of the mobile phone when the short-side direction of the rectangleis a substantially horizontal direction in the case where the mobilephone shown in FIG. 3A is seen from the front. Note that a substantiallyperpendicular direction refers to a direction where a short-sidedirection of a rectangle is inclined in the range of −20° to 20° from aperpendicular direction in the case where the mobile phone is seen fromthe front, as shown in FIG. 3A, for example. In addition, an obliquedirection refers to a direction where a short-side direction of arectangle is inclined in the range of −25° to 25° from a 45° directionwith respect to a horizontal direction or a perpendicular direction inthe case where the mobile phone is seen from the front, as shown in FIG.3A, for example. Further, a substantially horizontal direction refers toa direction where a short-side direction of a rectangle is inclined inthe range of −20° to 20° from a horizontal direction in the case wherethe mobile phone is seen from the front, as shown in FIG. 3A, forexample. Note that with respect to the signals in accordance with thedegree of the gradient of the mobile phone in the gradient detectionportion, more functions may be set separately. In this embodiment mode,examples of switching of the functions in accordance with the functionused by the user when the short-side direction of the rectangle is alongitudinal direction in the case where the display surface of themobile phone is seen from the front, a long-side direction is fixed, andthe short-side direction is inclined are described by separatelydescribing the case where the short side of the rectangle is inclined ina substantially perpendicular direction, the case where the short sideof the rectangle is inclined in an oblique direction, and the case wherethe short side of the rectangle is inclined in a substantiallyhorizontal direction. Note that the reference numerals used in theperspective views of the mobile phone shown in FIGS. 3B to 3D are thesame as the reference numerals used for the mobile phone shown in FIG.2A, so that description thereof is omitted.

Note that in this specification, the state of the mobile phone in FIG.3B is referred to as a first state (or a lateral and perpendicularstate); the state of the mobile phone in FIG. 3C is referred to as asecond state (or a lateral and oblique state); and the state of themobile phone in FIG. 3D is referred to as a third state (or a lateraland horizontal state). Note that the present invention is not limited tothe states in FIGS. 3B to 3D, and any state may be used as long asfunctions are switched in accordance with a gradient which is suitablefor the function of the mobile phone.

Note that in this specification, terms such as “first”, “second”,“third”, and “N^(th)” (N is a natural number) are used in order to avoidconfusion among components, and the terms do not limit the componentsnumerically.

Functions of the mobile phone in the first state shown in FIG. 3B aredescribed in FIGS. 4A to 4D. The mobile phone shown in FIG. 4A isdescribed assuming that the mobile phone receives television broadcaststo display images or an image function is used based on moving imagedisplay stored in the memory portion when the user uses the mobilephone. In the perspective view shown in FIG. 4A, the reference numeralsused for the mobile phone shown in FIG. 2A are used in a manner similarto that of FIG. 3B. A plurality of pixels are provided in the displayportion 201 and a display element and an optical sensor are provided ineach of the plurality of pixels, as described in FIG. 1.

In the case of utilizing the image function on the mobile phone, thereis a function of displaying necessary images in a user-friendly way as afunction used by the user. The above function is used by the user withthe housing of the mobile phone set in a longitudinal direction, thatis, with a gradient where a short-side direction of a rectangle is alongitudinal direction (a perpendicular direction) in the case where thedisplay surface is seen from the front. When the function is describedwith reference to a schematic view of a display surface of the mobilephone shown in FIG. 4B, display 253 of a desired image (e.g., an imageof a television broadcast) is provided in the display portion 201. Theuser who uses the image function on the mobile phone can watch images oftelevision broadcasts by using most of the portions of the displaysurface.

In the present invention, a gradient detection portion is providedinside the mobile phone, signals which are output from the arithmeticcircuit to the display portion control circuit are switched by signalsin accordance with the degree of the gradient of the mobile phone in thegradient detection portion, and display is performed on the displayportion in which the pixel circuit portion is provided. That is, in thegradient detection portion, when the mobile phone detects the gradientof the housing in the case of being provided with the housing as shownin FIG. 4A, the arithmetic circuit performs processing so that displaywith the display element provided in each pixel is performed as shown inFIG. 4B; therefore, the user can watch images by using most of theportions of the display surface with the display element provided ineach pixel.

Note that in the schematic view in the case where the image function onthe mobile phone shown in FIG. 4B is utilized, the display 252 of thedesired image is shown in the display portion 201. The schematic view inthe case where the image function on the mobile phone shown in FIG. 4Bis utilized can be described by dividing the display portion of themobile phone into the segment display region 211 and the image displayregion 212, as shown in FIG. 4C. Alternatively, the schematic view inthe case where the image function on the mobile phone shown in FIG. 4Bis utilized can be described by dividing the display portion of themobile phone into the segment display region 211, the image displayregion 212, and the input key display region 213, as shown in FIG. 4D.When the user watches images of television broadcasts on the mobilephone, selection of broadcast stations is performed. Thus, it ispreferable to provide the input key display region 213 becauseconvenience can be improved. The present invention is not limited to theabove display region; however, by using a structure where a displayelement and an optical sensor are provided in each pixel and a structurewhere a gradient detection portion is provided, the display region canbe optimized depending on functions in accordance with usability for theuser. Note that although the example in which the segment display region211 is displayed taking usability of the mobile phone into considerationis shown in FIG. 4B to FIG. 4D, the image function can be used withoutparticularly displaying the segment display region 211.

Note that a segment display region refers to a region for displayingsigns or the like which show a reception condition of radio signals,capacity of a battery, and a function displayed by a mobile phone.Alternatively, a segment display region may refer to a region fornotifying simple character information with a telop or the like.

Functions of the mobile phone in the second state shown in FIG. 3C aredescribed in FIGS. 5A to 5C. The mobile phone shown in FIG. 5A isdescribed assuming that a function of transmitting and receiving e-mailor the like through the Internet, in particular, a function of editingtext of e-mail or the like (hereinafter referred to as an editingfunction) is used when the user uses the mobile phone. In theperspective view shown in FIG. 5A, the reference numerals used for themobile phone shown in FIG. 2A are used in a manner similar to that ofFIG. 3C. A plurality of pixels are provided in the display portion 201and a display element and an optical sensor are provided in each of theplurality of pixels, as described in FIG. 1.

In the case of utilizing the editing function on the mobile phone, afunction of inputting desired characters is used as a function used bythe user. As shown in FIG. 5A, the above function is used by the userwith the housing of the mobile phone set in a lateral and inclined in anoblique direction, that is, with a gradient where a short-side directionof a rectangle is a longitudinal direction in the case where the displaysurface is seen from the front and with a long-side direction fixed anda short-side direction inclined. When the function is described withreference to a schematic view of a display surface of the mobile phoneshown in FIG. 5B, display 254 of input characters and the display 252 ofa character input key are provided in the display portion 201. The userwho uses the editing function on the mobile phone can select desiredcharacters with the character input key and can input characters whileseeing display of the input characters.

In the present invention, a gradient detection portion is providedinside the mobile phone; signals which are output from the arithmeticcircuit to the display portion control circuit are switched by signalsin accordance with the degree of the gradient of the mobile phone in thegradient detection portion; and display is performed on the displayportion in which the pixel circuit portion is provided. That is, in thegradient detection portion, when the mobile phone detects the fact thatthe housing is in the state where a short-side direction of a rectangleis a longitudinal direction in the case where the display surface of themobile phone is seen from the front, a long-side direction is fixed, andthe short-side direction is inclined as shown in FIG. 5B, the arithmeticcircuit performs processing so that display with the display elementprovided in each pixel is performed as shown in FIG. 5B, and the kind,size, or arrangement of the input key can be varied by the opticalsensor provided in each pixel. Therefore, the display region of theinput key can be minimized in accordance with the function used by theuser, so that the size and arrangement of the input key can beoptimized.

In particular, in the case of utilizing the editing function on themobile phone, time for inputting characters can be shortened byproviding the input key with QWERTY layout, as shown in FIG. 5B. Notethat the layout of the input key is not limited to QWERTY layout, andDvorak layout or given layout of the input key by the user can be usedin accordance with a language or an intended purpose. As describedabove, in the mobile phone of the present invention, the display elementand the optical sensor are provided in the display portion, thearithmetic circuit performs processing in accordance with signals fromthe gradient detection portion, and the kind, size, or arrangement ofthe input key can be varied by the optical sensor provided in eachpixel. Therefore, unlike an input key which has predetermined kind,size, or arrangement, such as a built-in operation key, convenience forusers can be improved.

Note that in the schematic view in the case where the editing functionof the mobile phone shown in FIG. 5B is utilized, the display 254 of theinput characters and the display 252 of the character input key areshown in the display portion 201. The schematic view in the case wherethe editing function of the mobile phone shown in FIG. 5B is utilizedcan be described by dividing the display portion of the mobile phoneinto the segment display region 211, the input key display region 213,and a character display region 214, as shown in FIG. 5C. The presentinvention is not limited to the above display region; however, by usinga structure where a display element and an optical sensor are providedin each pixel and a structure where a gradient detection portion isprovided, the display region can be optimized depending on functions inaccordance with usability for the user. Note that although the examplein which the segment display region 211 is displayed taking usability ofthe mobile phone into consideration is shown in FIG. 5B and FIG. 5C, theediting function can be used without particularly displaying the segmentdisplay region 211.

Functions of the mobile phone in the third state shown in FIG. 3D aredescribed in FIGS. 6A to 6C. The mobile phone shown in FIG. 6A isdescribed assuming that the user uses the editing function, though ithas been described in FIG. 5A. In the perspective view shown in FIG. 6A,the reference numerals used for the mobile phone shown in FIG. 2A areused in a manner similar to that of FIG. 3D. A plurality of pixels areprovided in the display portion 201 and a display element and an opticalsensor are provided in each of the plurality of pixels, as described inFIG. 1.

In the case of utilizing the editing function on the mobile phone, afunction of inputting desired characters is used as a function used bythe user. The mobile phone utilizing the editing function, which isshown in FIGS. 6A to 6C, differs from the mobile phone utilizing theediting function, which is described in FIGS. 5A to 5C, in that theconvenience of the function of inputting desired characters is improved.That is, a function of displaying a character input key by using most ofthe portions of the display portion is described. As shown in FIG. 6A,the above function is used by the user with the housing of the mobilephone set in a lateral direction, that is, with a gradient where ashort-side direction of a rectangle is a longitudinal direction in thecase where the display surface is seen from the front and with along-side direction fixed and the short-side direction inclinedhorizontally. When the function is described with reference to aschematic view of a display surface of the mobile phone shown in FIG.6B, the display 254 of input characters and the display 252 of thecharacter input key are provided in the display portion 201. The userwho uses the editing function on the mobile phone can select desiredcharacters with the character input key and can input characters whileseeing display of the input characters.

In the present invention, a gradient detection portion is providedinside the mobile phone; signals which are output from the arithmeticcircuit to the display portion control circuit are switched by signalsin accordance with the degree of the gradient of the mobile phone in thegradient detection portion; and display is performed on the displayportion in which the pixel circuit portion is provided. That is, in thegradient detection portion, when the mobile phone detects the fact thatthe housing is in the state where a short-side direction of a rectangleis a longitudinal direction in the case where the display surface isseen from the front, a long-side direction is fixed, and the short-sidedirection is inclined horizontally as shown in FIG. 6B, the arithmeticcircuit performs processing so that display with the display elementprovided in each pixel is performed as shown in FIG. 6B, and the kind,size, or arrangement of the input key can be varied by the opticalsensor provided in each pixel. Therefore, the display region of theinput key can be minimized in accordance with the function used by theuser, so that the size and arrangement of the input key can beoptimized.

In the case of utilizing the editing function on the mobile phone, asdescribed in FIG. 5B, time for inputting characters can be shortened byproviding the input key with QWERTY layout as shown in FIG. 6B. Inparticular, in the mobile phone shown in FIG. 6B, the mobile phone is inthe state where a short-side direction of a rectangle is a longitudinaldirection (a perpendicular direction) in the case where the displaysurface is seen from the front, a long-side direction is fixed, and theshort-side direction is inclined horizontally, and the size of the inputkey can be made larger. Therefore, characters can be input in a mannersimilar to that of a keyboard of a laptop computer or a desktopcomputer, so that time for inputting characters by the user can beconsiderably shortened. Note that the layout of the input key is notlimited to QWERTY layout, and Dvorak layout or given layout of the inputkey by the user can be used in accordance with a language or an intendedpurpose. As described above, in the mobile phone of the presentinvention, the display element and the optical sensor are provided inthe display portion, the arithmetic circuit performs processing inaccordance with signals from the gradient detection portion, and thekind, size, or arrangement of the input key can be varied by the opticalsensor provided in each pixel. Therefore, unlike an input key which haspredetermined kind, size, or arrangement, such as a built-in operationkey, convenience for users can be improved.

Note that in the schematic view in the case where the editing functionof the mobile phone shown in FIG. 6B is utilized, the display 254 of theinput characters and the display 252 of the character input key areshown in the display portion 201. The schematic view in the case wherethe editing function of the mobile phone shown in FIG. 6B is utilizedcan be described by dividing the display portion of the mobile phoneinto the segment display region 211, the input key display region 213,and the character display region 214, as shown in FIG. 6C. The presentinvention is not limited to the above display region; however, by usinga structure where a display element and an optical sensor are providedin each pixel and a structure where a gradient detection portion isprovided, the display region can be optimized depending on functions inaccordance with usability for the user. Note that although the examplein which the segment display region 211 is displayed taking usability ofthe mobile phone into consideration is shown in FIG. 6B and FIG. 6C, theediting function can be used without particularly displaying the segmentdisplay region 211.

Note that although the input key display region 213 for displaying thecharacter input key is one region in the case of realizing the editingfunction on the mobile phone as shown in FIG. 5C and FIG. 6C, aplurality of input key display regions may be provided on the displaysurface, such as a first input key display region 213A and a secondinput key display region 213B, as shown in FIG. 7A. In the case ofdisplaying a plurality of input key display regions on the displaysurface, the plurality of input key display regions are preferablyinterposed between the segment display region 211 and the characterdisplay region 214, as shown in FIG. 7A. By providing the first inputkey display region 213A and the second input key display region 213B atopposite ends of the display surface as shown in FIG. 7A, the characterinput keys can be operated while the housing is held by both hands asshown in FIG. 7B, so that time for inputting characters can be shortenedwith the housing held up.

As described above, in the mobile phone of the present invention, thedisplay element and the optical sensor are provided in each of theplurality of pixels; and functions used in the mobile phone, inparticular, functions related to display and input on the displaysurface are switched by the arithmetic circuit in accordance withsignals from the gradient detection portion. Therefore, a mobile phonewhich can be used without hampering convinience can be provided.Further, a mobile phone which optimizes the size or arrangement of thedisplay portion in which optical sensors are provided depending onfunctions of a mobile phone to be used and an operating method of themobile phone, so that operability can be improved.

Note that this embodiment mode can be implemented in combination withany technical component in other embodiment modes in this specification.

Embodiment Mode 2

In this embodiment mode, examples of the structures of the pixel circuitportion 101, the display element driver circuit 102, and the opticalsensor driver circuit 103 which are provided around the display portionof the mobile phone used in the present invention are described. FIG. 8is a block diagram of the pixel circuit portion 101, the display elementdriver circuit 102, and the optical sensor driver circuit 103. In FIG.8, the display element driver circuit 102 includes a data line drivercircuit 320 and a scan line driver circuit 322. Further, the opticalsensor driver circuit 103 includes an optical sensor signal line drivercircuit 321 and an optical sensor scan line driver circuit 323 thatcontrol the driving of a reset transistor, a buffer transistor, and aselection transistor provided in each pixel.

The data line driver circuit 320 includes a shift register 320 a, alatch (A) 320 b, and a latch (B) 320 c. In the data line driver circuit320, a clock signal (CLK) and a start pulse (SP) are input to the shiftregister 320 a. The shift register 320 a sequentially generates timingsignals based on the clock signal (CLK) and the start pulse (SP) andsupplies the timing signals to a circuit in the subsequent stage.

Note that amplitude voltage of the timing signals from the shiftregister 320 a may be amplified by a buffer or the like (not shown) andthe amplified timing signals may be sequentially supplied to the circuitin the subsequent stage. Since many circuits or elements are connectedto wirings to which the timing signals are supplied, load capacitance(parasitic capacitance) is large. In order to prevent generation of“delay” in rising or falling of the timing signals due to this largeload capacitance, the buffer is provided.

FIG. 9A shows an example of a circuit diagram of the pixel circuitportion 101. The pixel circuit portion 101 includes signal lines DL1 toDLy, scan lines SL1 to SLx, capacitor lines CL1 to CLx, reset scan linesRL1 to RLx, optical sensor output wirings OL1 to OLy, and an opticalsensor power supply line VB.

The pixel circuit portion 101 includes the plurality of pixels 110. Eachof the plurality of pixels 110 includes any one of the signal lines DL1to DLy, any one of the scan lines SL1 to SLx, any one of the capacitorlines CL1 to CLx, any one of the reset scan lines RL1 to RLx, any one ofthe optical sensor output wirings OL1 to OLy, and the optical sensorpower supply line VB. Each of the optical sensor output wirings OL1 toOLy is connected to a constant current power source 1000. Further, eachof the plurality of pixels 110 includes a display element portion 1001having a display element and an optical sensor portion 1002 having anoptical sensor.

FIG. 9B shows the structures of the display element portion 1001 and theoptical sensor portion 1002. The display element portion 1001 includes apixel transistor 1005, a storage capacitor 1003, and a liquid crystalelement 1004. The optical sensor portion 1002 includes a resettransistor 1010, a buffer transistor 1011, a selection transistor 1012,and a photodiode 1013. Note that a signal line DL refers to any one ofthe signal lines DL1 to DLy. In addition, a scan line SL refers to anyone of the scan lines SL1 to SLx. Further, a capacitor line CL refers toany one of the capacitor lines CL1 to CLx. Furthermore, a reset scanline RL refers to any one of the reset scan lines RL1 to RLx. Moreover,an optical sensor output wiring OL refers to any one of the opticalsensor output wirings OL1 to OLy.

Note that although a liquid crystal element is described as an exampleof a display element in this embodiment mode, the present invention isnot limited to this. An EL element (an organic EL element, an inorganicEL element, or an EL element containing an organic material and aninorganic material), or an electrophoretic element may be used.

Note that in this embodiment mode, a photodiode is described as anexample of an optical sensor. Further, a connection between thephotodiode and a transistor for reading light incident on the photodiodeis described as an example, and any circuit structure may be used aslong as it is a circuit structure for outputting electric signalsobtained by the incidence of light on the photodiode.

The liquid crystal element 1004 includes a pixel electrode, a counterelectrode, and a liquid crystal layer provided therebetween. A gate ofthe pixel transistor 1005 is connected to the scan line SL (any one ofSL1 to SLx). In addition, one of terminals which correspond to a sourceand a drain of the pixel transistor 1005 is connected to the signal lineDL, and the other thereof is connected to the liquid crystal element1004 and the storage capacitor 1003.

A gate of the reset transistor 1010 is connected to the reset scan lineRL (any one of RL1 to RLx). A terminal which corresponds to a source ofthe reset transistor 1010 is connected to the optical sensor powersupply line VB. The optical sensor power supply line VB is always keptat a certain potential (a reference potential). A terminal whichcorresponds to a drain of the reset transistor 1010 is connected to thephotodiode 1013 and a terminal which corresponds to a gate of the buffertransistor 1011.

Although not shown, the photodiode 1013 includes a cathode electrode, ananode electrode, and a photoelectric conversion layer providedtherebetween. The drain of the reset transistor 1010 is also connectedto the anode electrode or the cathode electrode of the photodiode 1013.

A terminal which corresponds to a drain of the buffer transistor 1011 isconnected to the optical sensor power supply line VB and is always keptat a certain reference potential. In addition, a terminal whichcorresponds to a source of the buffer transistor 1011 is connected toone of a source and a drain of the selection transistor 1012.

A gate of the selection transistor 1012 is connected to the scan line SL(any one of SL1 to SLx). In addition, one of terminals which correspondto the source and the drain of the selection transistor 1012 isconnected to the source of the buffer transistor 1011 as describedabove, and the other thereof is connected to the optical sensor outputwiring OL (any one of OL1 to OLy). Each of the optical sensor outputwirings (OL1 to OLy) is connected to the constant current power source1000 and is always supplied with certain current.

Although the case where the pixel transistor 1005 and the selectiontransistor 1012 have the same polarity is described in this embodimentmode, the structure of the pixel circuit portion 1001 is not limited tothis.

As described in this embodiment mode, in the mobile phone of the presentinvention, the display element and the optical sensor are provided ineach of the plurality of pixels. Further, as described in EmbodimentMode 1, functions used in the mobile phone, in particular, functionsrelated to display and input on the display surface are switched by anarithmetic circuit in accordance with signals from a gradient detectionportion. Therefore, a mobile phone which can be used without hamperingconvinience can be provided. Further, a mobile phone which optimizes thesize or arrangement of the display portion in which optical sensors areprovided depending on functions of a mobile phone to be used and anoperating method of the mobile phone, so that operability can beimproved.

Note that this embodiment mode can be implemented in combination withany technical component in other embodiment modes in this specification.

Embodiment Mode 3

In this embodiment mode, a method for manufacturing each transistorincluded in the pixel circuit portion over a substrate having aninsulating surface is described in detail. First, as shown in FIG. 10A,a first insulating film 702 a and a second insulating film 702 b areformed over a substrate 701. A first semiconductor layer 703, a secondsemiconductor layer 704, a third semiconductor layer 705, a fourthsemiconductor layer 706, and a fifth semiconductor layer 707 are formedover the second insulating film 702 b.

As the substrate 701, a glass substrate, a quartz substrate, a ceramicsubstrate, a plastic substrate, a semiconductor substrate, a sapphiresubstrate, a metal substrate, or the like can be used. The semiconductorlayers can be formed using single crystal silicon, germanium, a compoundsemiconductor such as gallium arsenide or indium phosphide, or the like.

Further, the substrate 701 is attached to the first semiconductor layer703, the second semiconductor layer 704, the third semiconductor layer705, the fourth semiconductor layer 706, and the fifth semiconductorlayer 707 with the first insulating film 702 a and the second insulatingfilm 702 b interposed therebetween. An example of attaching thesubstrate to the semiconductor layers is described with reference toFIGS. 11A to 11F. FIGS. 11A to 11F are cross-sectional views showingsteps of attaching the substrate to the semiconductor layers in thisembodiment mode. Note that in this embodiment mode, size which isdifferent from actual size is used in FIGS. 11A to 11F for convenience.

First, as shown in FIG. 11A, a first insulating film 1102 is formed overone of surfaces of a semiconductor substrate 1101. As the semiconductorsubstrate, a single crystal silicon substrate, a germanium substrate, acompound semiconductor substrate formed using gallium arsenide or indiumphosphide, or the like can be used. Further, the first insulating film1102 is the same layer as the second insulating film 702 b shown inFIGS. 10A to 10D and can be formed with a structure of two or morelayers by stacking layers formed using silicon nitride, silicon nitrideoxide, or silicon oxynitride. The first insulating film 1102 can beformed by chemical vapor deposition (CVD), sputtering, or the like. Thefirst insulating film 1102 is preferably formed to a thickness greaterthan or equal to 50 nm and less than or equal to 200 nm. Note thatchemical vapor deposition (CVD) in this specification includes plasmaenhanced CVD, thermal CVD, and photo CVD in its category.

Note that silicon oxynitride refers to a substance which contains moreoxygen than nitrogen and contains oxygen, nitrogen, silicon, andhydrogen at concentrations ranging from 55 to 65 atomic %, 0.5 to 20atomic %, 25 to 35 atomic %, and 0.1 to 10 atomic %, respectively.Further, silicon nitride oxide refers to a substance which contains morenitrogen than oxygen and contains oxygen, nitrogen, silicon, andhydrogen at concentrations ranging from 5 to 30 atomic %, 20 to 50atomic %, 25 to 35 atomic %, and 15 to 25 atomic %, respectively.

Next, as shown in FIG. 11B, ions which are accelerated by an electricfield are introduced into the semiconductor substrate 1101 byirradiating the semiconductor substrate 1101 with an ion beam of theions which are accelerated by an electric field through the firstinsulating film 1102, so that a region 1103 into which hydrogen isintroduced is formed to reach a predetermined depth from the one of thesurfaces of the semiconductor substrate 1101.

Next, as shown in FIG. 11C, a bonding layer 1104 is formed over thefirst insulating film 1102. The bonding layer 1104 is provided on asurface where the semiconductor substrate 1101 forms a bond with a basesubstrate. The bonding layer 1104 may have a single layer structure or alayered structure of two or more layers, and a surface which forms abond with the substrate 1101 (hereinafter referred to as a bondingsurface) preferably has a smooth surface and forms a hydrophilicsurface.

The bonding layer 1104, the bonding surface of which, has a smoothsurface and forms a hydrophilic surface can be formed using siliconoxide containing hydrogen, silicon nitride containing hydrogen, siliconnitride containing oxygen and hydrogen, silicon oxynitride, siliconnitride oxide, or the like.

As silicon oxide containing hydrogen, for example, silicon oxidemanufactured by chemical vapor deposition using organosilane ispreferable. This is because the base substrate and a single crystalsemiconductor layer can be firmly bonded to each other by using thebonding layer 1104 formed using organosilane, for example, a siliconoxide film. As organosilane, a silicon containing compound such astetraethoxysilane (abbreviation: TEOS) (chemical formula: Si(OC₂H₅)₄),tetramethylsilane (abbreviation: TMS) (chemical formula: Si(CH₃)₄),tetramethylcyclotetrasiloxane (abbreviation: TMCTS),octamethylcyclotetrasiloxane (abbreviation: OMCTS), hexamethyldisilazane(abbreviation: HMDS), triethoxysilane (chemical formula: SiH(OC₂H₅)₃),or trisdimethylaminosilane (chemical formula: SiH(N(CH₃)₂)₃) can beused.

Note that in the case of forming the bonding layer 1104 by using siliconoxide, the bonding layer 1104 can be formed by CVD using monosilane,disilane, or trisilane as a source gas. In addition, a silicon oxidelayer which functions as the bonding layer may be a thermal oxidationfilm and preferably contains chlorine.

Silicon nitride containing hydrogen can be formed by plasma enhanced CVDusing a silane gas and an ammonia gas. Further, hydrogen may be added tothe above gases. Silicon nitride containing oxygen and hydrogen can beformed by plasma enhanced CVD using a silane gas, an ammonia gas, and anitrous oxide gas. In each case, silicon oxide, silicon oxynitride, orsilicon nitride oxide, which is manufactured by chemical vapordeposition such as plasma enhanced CVD, low pressure CVD, or atmosphericpressure CVD, which uses a silane gas or the like as a source gas, canbe used as long as it contains hydrogen. In deposition by CVD,temperature at which degassing does not occur from the region 1103 intowhich hydrogen is introduced, which is formed in the semiconductorsubstrate 1101, is used. For example, deposition temperature ispreferably lower than or equal to 350° C. Note that in heat treatmentfor cleaving the semiconductor layer from the semiconductor substrate1101, heat treatment temperature which is higher than depositiontemperature by CVD is used. In each case, the bonding layer 1104 may beany layer as long as it has a smooth surface and a surface with ahydroxy group.

The thickness of the bonding layer 1104 can be greater than or equal to10 nm and less than or equal to 200 nm. Preferably, the thickness of thebonding layer 1104 is greater than or equal to 10 nm and less than orequal to 100 nm, more preferably greater than or equal to 20 nm and lessthan or equal to 50 nm.

Next, as shown in FIG. 11D, the semiconductor substrate 1101 is disposedin contact with a substrate 1105 which is separately prepared. Bydisposing a surface of the bonding layer 1104 formed over thesemiconductor substrate 1101 in contact with a surface of the substrate1105, the semiconductor substrate 1101 and the substrate 1105 are bondedto each other. A hydrogen bond or van der Waals force acts on this bond.A hydrogen bond is formed when a surface of the substrate has ahydrophilic property, a hydroxy group or a water molecule functions asan adhesive agent, the water molecule is diffused by heat treatment, anda residual component forms a silanol group (Si—OH). Further, thisbonding portion forms a covalent bond by formation of a siloxane bond(O—Si—O) due to release of hydrogen, so that the semiconductor substrate1101 and the substrate 1105 are firmly bonded to each other.

The substrate 1105 is the same as the substrate 701 shown in FIG. 10Aand can be a substrate having an insulating surface. As the substrate1105, a glass substrate is preferably used. For example, a large-areamother glass substrate called the sixth generation (1500 mm×1850 mm),the seventh generation (1870 mm×2200 mm), or the eighth generation (2200mm×2400 mm) is used. By manufacturing the semiconductor substrate withthe large-area mother glass substrate used as the base substrate, thearea of the mother glass substrate can be made larger. Accordingly, thenumber of display panels which can be manufactured from one substrate(the number of panels obtained per substrate) can be increased, so thatproductivity can be improved.

A surface of any of various glass substrates which are used in theelectronics industry, such as aluminosilicate glass substrates,aluminoborosilicate glass substrates, and barium borosilicate glasssubstrates, preferably has a polished surface because flatness isextremely favorable. By bonding the polished surface of the glasssubstrate to a single crystal semiconductor substrate or the bondinglayer formed on the single crystal semiconductor substrate, bondingdefects can be reduced. The glass substrate may be polished with, forexample, cerium oxide. By performing the polishing treatment, the singlecrystal semiconductor substrate can be attached to a substantiallyentire surface of the glass substrate, which includes end regions on themain surface.

Note that in order to favorably bond the substrate 1105 and the bondinglayer 1104 to each other, bonding surfaces may be activated. Forexample, one or both of the bonding surfaces are irradiated with anatomic beam or an ion beam. In the case of utilizing an atomic beam oran ion beam, an inert gas neutral atomic beam or an inert gas ion beamof argon or the like can be used. Alternatively, plasma irradiation orradical treatment for activating the bonding surfaces can be performed.With such surface treatment, different kinds of materials can be easilybonded to each other even at a temperature lower than or equal to 400°C.

After the substrate 1105 and the semiconductor substrate 1101 are bondedto each other with the bonding layer 1104 interposed therebetween (seeFIG. 11D), one or both of heat treatment and pressure treatment arepreferably performed. By performing heat treatment and/or pressuretreatment, the substrate 1105 and the semiconductor substrate 1101 canbe bonded to each other more firmly. The heat treatment is performed attemperature lower than or equal to the allowable temperature limit ofthe substrate 1105. The pressure treatment is performed taking thepressure resistance of the substrate 1105 and the semiconductorsubstrate 1101 into consideration so that pressure can be applied in aperpendicular direction to the bonding surfaces.

Next, as shown in FIG. 11E, by performing the heat treatment on thesemiconductor substrate 1101, the semiconductor substrate 1101 iscleaved with the region 1103 used as a cleavage plane. The heattreatment is preferably performed at a temperature higher than or equalto the deposition temperature of the bonding layer 1104 and lower thanor equal to the allowable temperature limit of the substrate 1105. Forexample, by performing the heat treatment at a temperature higher thanor equal to 400° C. and lower than or equal to 700° C., the volume ofmicrovoids formed in the region 1103 is changed, so that cleavage isperformed along the region 1103. Since the bonding layer 1104 is bondedto the substrate 1105, a semiconductor layer which is separated from thesemiconductor substrate 1101 is firmly fixed to the substrate 1105, anda semiconductor layer which has the same crystal structure and crystalorientation as the semiconductor substrate can be left on the substrate1105, as shown in FIG. 11F.

The heat treatment at the temperature higher than or equal to 400° C.and lower than or equal to 700° C. may be performed sequentially withthe same apparatus as the heat treatment for improving the bondingstrength, or may be performed with a different apparatus. For example,after heat treatment is performed in a furnace at 200° C. for 2 hours,the temperature is increased to around 600° C. and held for 2 hours, thetemperature is decreased to a temperature range of 400° C. to roomtemperature, and then the substrate is taken out of the furnace.Alternatively, heat treatment may be performed with a temperatureincreased from room temperature. Further alternatively, after heattreatment may be performed in a furnace at 200° C. for 2 hours, heattreatment may be performed at a temperature range of 600° C. to 700° C.with a rapid thermal annealing (RTA) apparatus for 1 minute to 30minutes (e.g., at 600° C. for 7 minutes, or at 650° C. for 7 minutes).

By performing the heat treatment at the temperature higher than or equalto 400° C. and lower than or equal to 700° C., the bond between thebonding layer 1104 and the substrate 1105 transfers from the hydrogenbond to a covalent bond; an element added to the region 1103precipitates to raise the pressure; and the semiconductor substrate 1101is cleaved so that a semiconductor layer can be formed. After the heattreatment is performed, one of the substrate 1105 and the semiconductorsubstrate 1101 is provided over the other thereof, and the substrate1105 and the semiconductor substrate 1101 can be separated from eachother without application of large force. For example, the substrate1105 and the semiconductor substrate 1101 can be easily separated fromeach other by lifting the substrate provided over the other by a vacuumchuck. In this case, if the substrate provided below the other is fixedby a vacuum chuck or a mechanical chuck, deviation in a horizontaldirection is not generated, so that both the substrate 1105 and thesemiconductor substrate 1101 can be separated from each other.

Note that at this time, in order to improve the crystallinity of asemiconductor layer 1106 formed on the substrate 1105, it is possible toirradiate a surface of the semiconductor layer with a laser beam. Byirradiating the surface of the semiconductor layer with a laser beam,defects in the semiconductor layer can be reduced.

Further, in order to improve the flatness of the surface of thesemiconductor layer 1106 formed on the substrate 1105, it is possible toperform either dry etching or wet etching. By performing either dryetching or wet etching, part of the semiconductor layer 1106 is removed,so that roughness of the surface can be reduced.

Further, in order to improve the crystallinity of the surface of thesemiconductor layer 1106 formed on the substrate 1105, it is possible toperform heat treatment. For example, heat treatment is preferablyperformed at a temperature higher than or equal to 500° C. and lowerthan or equal to 700° C. With this heat treatment, defects anddistortion of the semiconductor layer 1106, which are not reduced byirradiation with a laser beam, can be reduced and relieved.

With the above method, the semiconductor layer 1106 provided on thesubstrate 1105 with an insulating film interposed therebetween, which isshown in FIG. 11F, can be formed. Note that the method shown in FIGS.11A to 11F is just an example, and the present invention is not limitedto this. The semiconductor layer 1106 can be formed using a differentmethod.

FIG. 10A is described again. A gate insulating film 708 which covers thefirst semiconductor layer 703, the second semiconductor layer 704, thethird semiconductor layer 705, the fourth semiconductor layer 706, andthe fifth semiconductor layer 707 separated into island shapes and thesecond insulating film 702 b is formed. The gate insulating film 708 isformed by plasma enhanced CVD or sputtering. In addition, a firstconductive film 709 a and a second conductive film 709 b for forming agate electrode are formed over the gate insulating film 708.

The gate insulating film 708 can be formed using a single layerstructure or a layered structure of any one of or a plurality of siliconoxide, silicon nitride, silicon oxynitride, and silicon nitride oxide.

Each of the first conductive film 709 a and the second conductive film709 b can be formed using an element such as tantalum, tungsten,titanium, molybdenum, aluminum, copper, chromium, or niobium, or analloy material or a compound material containing such an element as itsmain component. In this embodiment mode, the first conductive film 709 ais formed using tantalum nitride and the second conductive film 709 b isformed using tungsten.

Next, as shown in FIG. 10B, resist masks 710 to 715 are formed and firstetching treatment for forming gate electrodes is performed. Although theetching is not limited to a particular method, an ICP (inductivelycoupled plasma) etching is preferably used.

In the above etching conditions, end portions of the gate electrodes canhave tapered shapes due to the shapes of the resist mask and anadvantageous effect of bias voltage applied on the substrate side.Further, since the etching is performed without leaving a residue overthe gate insulating film, surfaces to which the gate insulating film 708is exposed are partly etched by over-etching treatment. Thus, throughthe first etching treatment, conductive films 716 to 721 (firstconductive films 716 a to 721 a and second conductive films 716 b to 721b) with first shapes, which are formed of first conductive films andsecond conductive films, and a gate insulating film 722 are formed.

Then, as shown in FIG. 10C, first doping treatment is performed so thatan impurity which imparts n-type conductivity (a donor) is added. Thedoping is performed by either an ion doping method or an ionimplantation method. As an impurity element which imparts n-typeconductivity, an element which belongs to Group 15, typically,phosphorus (P) or arsenic (As) is used. The conductive films with thefirst shapes are used as masks. Thus, first impurity regions 723 to 727are formed.

Second etching treatment shown in FIG. 10D is isotropic etchingtreatment by ICP (inductively coupled plasma) etching and conductivefilms 728 to 733 (first conductive films 728 a to 733 a and secondconductive films 728 b to 733 b) with second shapes are formed.Reference numeral 739 denotes a gate insulating film. Regions of thegate insulating film 739, which are not covered with the conductivefilms 728 to 733 with the second shapes, are reduced in thicknessbecause they are etched.

Subsequently, second doping treatment is performed. The dosage is setlower than that in the first doping treatment, and an impurity whichimparts n-type conductivity (a donor) is added in a condition of highacceleration voltage. Second impurity regions 734 to 738 are formedinside the first impurity regions formed in the island-shapedsemiconductor layers in FIG. 10C. This doping is performed in such amanner that an impurity element is added to regions below the conductivefilms 728 a to 733 a with the second shapes by using the conductivefilms 728 b to 733 b with the second shapes as masks with respect to theimpurity element.

Then, as shown in FIG. 12A, third etching treatment is performed to etchthe gate insulating film. Accordingly, the conductive films 728 a to 733a with the second shapes are also etched and end portions thereof aredecreased due to recession, so that conductive films 740 to 745 (firstconductive films 740 a to 745 a and second conductive films 740 b to 745b) with third shapes are formed. Reference numeral 746 denotes aremaining gate insulating film. The etching may be further performed sothat the surface of the semiconductor layers is exposed.

Resist masks 758 to 760 are formed with respect to p-channel TFTs asshown in FIG. 12B, and an impurity which imparts p-type conductivity (anacceptor) is added to the island-shaped semiconductor layers for formingthe p-channel TFTs. By performing the doping, third impurity regions 767a, 767 b, 767 c, 768 a, 768 b, and 768 c are formed in the island-shapedsemiconductor layers. The impurity which imparts p-type conductivity(the acceptor) is selected from an element which belongs to Group 13,typically, boron (B) is used.

Through the above steps, the impurity regions are formed in thesemiconductor layers. After that, in a step shown in FIG. 12C, resistmasks 769 and 770 are formed and the conductive film 743 with the thirdshape, which is formed over the semiconductor layer 706 for forming thephotodiode, is removed. The conductive films 740, 741, 742, and 744 withthe third shapes serve as gate electrodes, and the conductive film 745with the third shape serves as a capacitor wiring.

Next, as shown in FIG. 13A, a first interlayer insulating film 771formed of a silicon nitride film or a silicon oxynitride film is formedby plasma enhanced CVD. Then, a step of activating the impurity elementadded to the respective island-shaped semiconductor layers is performedin order to control the conductivity type. The activation is preferablyperformed by thermal annealing using an annealing furnace.Alternatively, laser annealing or rapid thermal annealing (RTA) can beused.

A contact hole is formed in the first interlayer insulating film 771 andan optical sensor output wiring 772, a connection wiring 773, an opticalsensor power supply line 775, a connection wiring 777, a common wiring779, a source signal line 780, and a drain wiring 781 are formed usingaluminum (Al), titanium (Ti), tantalum (Ta), or the like. Further, theconnection wiring 777 extends over a photodiode 804 in order to shieldlight.

Then, over these wirings, a passivation film 782 and a second interlayerinsulating film 783 are formed. The passivation film 782 can be formedusing a silicon nitride film. Further, the second interlayer insulatingfilm 783 is formed using an organic resin. For an organic resin film,polyimide, acrylic, polyimide amide, or the like can be used.

Next, as shown in FIG. 13B, a contact hole which reaches the drainwiring 781 is formed in the second interlayer insulating film 783 andthe passivation film 782 to form a pixel electrode 784. In the case of atransmissive liquid crystal display device, the pixel electrode isformed using a transparent conductive film (indium tin oxide (ITO), analloy of indium oxide and zinc oxide (In₂O₃—ZnO), zinc oxide (ZnO) orthe like). In the case of a reflective liquid crystal display device,the pixel electrode is formed of a reflective film (a metal film ofaluminum or the like). Alternatively, in the case of a display devicehaving an EL element as a display element, the pixel electrode is formedusing a material used for an anode or a cathode of a light-emittingelement.

In this manner, a buffer transistor 801, a selection transistor 802, areset transistor 803, the photodiode 804, a pixel transistor 805 and astorage capacitor 806 can be formed.

The buffer transistor 801 is an n-channel transistor and has a channelformation region 810, a second impurity region 811 which is formed ofthe conductive film 740 with the third shape and overlaps with the gateelectrode (a gate overlapped drain (GOLD) region)), a second impurityregion 812 which is formed outside the gate electrode (a lightly dopeddrain (LDD) region), and a first impurity region 813 which functions asa source or a drain.

The selection transistor 802 is also an n-channel transistor and has achannel formation region 814, a second impurity region 815 which isformed of the conductive film 741 with the third shape and overlaps withthe gate electrode, a second impurity region 816 which is formed outsidethe gate electrode, and a first impurity region 817 which functions as asource or a drain.

The reset transistor 803 is a p-channel transistor and has a channelformation region 818 and third impurity regions 819 to 821 whichfunction as sources or drains.

The photodiode 804 has third regions 826 to 828 to which an impuritywhich imparts p-type conductivity is added, a first impurity region 825and second impurity regions 823 and 824 to which an impurity whichimparts n-type conductivity is added, and an intrinsic region 822 towhich an impurity is not added. Thus, the photodiode 804 has a so-calledpin-type structure. In addition, the first impurity region 825 is incontact with the connection wiring 777 and is connected to a drain sideof the reset transistor 803. Meanwhile, the third impurity region 828 isin contact with the common wiring 779.

The pixel transistor 805 has a channel formation region 829, a secondimpurity region 830 which overlaps with the gate electrode (a GOLDregion) formed of the conductive film 743 with the third shape and, asecond impurity region 831 which is formed outside the gate electrode(an LDD region), and first impurity regions 832, 833, and 834 whichfunction as sources or drains. Further, a semiconductor layer 835 whichfunctions as one of electrodes of the storage capacitor 806 issequentially formed from the first impurity regions and is provided withregions 836 and 837 to which an impurity is added at the sameconcentration as the second impurity region at end portions.

FIG. 14 is a top view of such a pixel circuit. In FIG. 14, line A-A′ andline B-B′ correspond to line A-A′ and line B-B′ shown in FIG. 13B,respectively. Further, reference numerals used in the top view of thepixel circuit shown in FIG. 14 are similar to those of the pixel portionshown in FIGS. 9A and 9B.

As described in this embodiment mode, in the mobile phone of the presentinvention, the display element and the optical sensor are provided ineach of a plurality of pixels and can be formed concurrently through asequence of steps. Further, as described in Embodiment Mode 1, functionsused in the mobile phone, in particular, functions related to displayand input on the display surface are switched by an arithmetic circuitin accordance with signals from a gradient detection portion. Therefore,a mobile phone which can be used without hampering convinience can beprovided. Further, a mobile phone which optimizes the size orarrangement of the display portion in which optical sensors are provideddepending on functions of a mobile phone to be used and an operatingmethod of the mobile phone, so that operability can be improved.

Note that this embodiment mode can be implemented in combination withany technical component in other embodiment modes in this specification.

Embodiment Mode 4

In this embodiment mode, a step of manufacturing the display portion ofthe mobile phone from the substrate over which components aremanufactured up to the pixel electrode and the transistors are formed inEmbodiment Mode 3 is described. In FIG. 15, a step in the case where atransmissive liquid crystal display device is used for the displayportion of the mobile phone is described. First, after the substrateover which the transistors in the state of FIG. 13B are formed ismanufactured in accordance with Embodiment Mode 3, a columnar spacer1401 is formed, as shown in FIG. 15. Then, an alignment film 1402 isformed so as to cover the spacer 1401 and rubbing treatment isperformed.

After a counter substrate 1403 is provided with a counter electrode 1404and an alignment film 1405, rubbing treatment is performed. Then, thesubstrate over which the transistors are formed and the countersubstrate are attached to each other. After that, a liquid crystalmaterial is injected between the both substrates to form a liquidcrystal layer 1406. In this manner, a display portion of an activematrix liquid crystal display device which includes a pixel circuitformed of an optical sensor and a display element, which is shown inFIG. 16, is completed. By providing a backlight unit 1501 as shown inFIG. 16, the display portion of the completed active matrix liquidcrystal display device can display images and can perform detection withthe optical sensor. The backlight unit 1501 includes, for example, alight source 1502, a diffusion plate 1503, and a light guide plate 1504.Light from the light source 1502 is diffused by the diffusion plate andis emitted on the liquid crystal layer side (on the counter substrateside) through the light guide plate. The light is transmitted throughthe transistors and is delivered to an object 1505 to which light isdelivered. In accordance with the existence or nonexistence of theobject 1505 to which light is delivered, the light is reflected ortransmitted and whether the light enters or does not enter thephotodiode is selected. Thus, the object to which light is delivered canbe read as an electric signal by the photodiode, which is an opticalsensor.

Note that as the light source, either a cold cathode fluorescent lamp ora light-emitting diode may be used. Note that as the backlight unit, abacklight unit where light-emitting diodes are provided over the entiresurface and are used as planar light sources may be used. In this case,it is also possible to use a structure where the diffusion plate and thelight guide plate are eliminated.

Note that by emitting the light from the light source 1502intermittently, detection can be performed by the photodiode, which isan optical sensor, with external light and light from the backlight unitseparated from each other, which is preferable.

Note that by forming the semiconductor layer included in the photodiode,which is an optical sensor, over a single crystal silicon substrate asdescribed in Embodiment Mode 3, the wavelength of light to be absorbedhas a peak of relative sensitivity around a wavelength of 900 nm. Inthis case, a structure may be used in which the light from the backlightunit is used as a first light source for the display element, which isvisible light, and the photodiode which is an optical sensor is used asa second light source which is near-infrared light for detectingreflected light. The first light source and the second light source canbe switched by a display control circuit to favorably display imageswith the display element and can improve sensitivity of light of thephotodiode which is an optical sensor, concurrently, which ispreferable.

Next, in FIG. 17, a step of manufacturing the display portion of themobile phone having an EL element as a display element, from thesubstrate over which the components are manufactured up to the pixelelectrode and the transistors are formed in Embodiment Mode 3 isdescribed. In FIG. 17, a step in the case where a so-called bottomemission-type EL element, which emits light from a side on which thetransistors are provided, is used for the display portion of the mobilephone is described. First, after the substrate over which thetransistors in the state of FIG. 13B are formed is manufactured inaccordance with Embodiment Mode 3, a light-emitting layer 1702 is formedover an electrode 1701 which serves as an anode, as shown in FIG. 17.Next, an electrode 1703 which serves as a cathode of the light-emittingelement is formed so as to cover the light-emitting layer 1702. Then, acounter substrate 1704 and the substrate over which the transistors areformed are attached to each other. In this manner, a display portion ofan active matrix light-emitting device which includes a pixel circuitformed of an optical sensor and a display element, which is shown inFIG. 17, is completed. By emitting light from the light-emitting layer1702 as shown in FIG. 18, the display portion of the completed activematrix light-emitting device can display images and can performdetection with the optical sensor. The light from the light-emittinglayer 1702 is emitted on a transistor substrate side. The light isdelivered to an object 1801 to which light is delivered. In accordancewith the existence or nonexistence of the object 1801 to which light isdelivered, the light is reflected or transmitted and whether the lightenters or does not enter the photodiode is selected. Thus, the object towhich light is delivered can be read as an electric signal by thephotodiode which is an optical sensor.

Note that by emitting the light from the light-emitting layer 1702intermittently, detection can be performed by the photodiode, which isan optical sensor, with external light and light from the light-emittinglayer separated from each other, which is preferable.

Note that by forming the semiconductor layer included in the photodiode,which is an optical sensor, over a single crystal silicon substrate asdescribed in Embodiment Mode 3, the wavelength of light to be absorbedhas a peak of relative sensitivity around a wavelength of 900 nm. Inthis case, a structure is preferably used in which a backlight unitwhich has a light source for emitting near-infrared light so that thephotodiode detects reflected light as well as visible light emitted fromthe light-emitting element is provided. By operating the light sourcefor emitting near-infrared light intermittently by a display controlcircuit, power consumption can be reduced and sensitivity of light ofthe photodiode which is an optical sensor can be improved concurrently,which is preferable.

Note that by forming the semiconductor layer included in the photodiode,which is an optical sensor, over a single crystal silicon substrate asdescribed in Embodiment Mode 3, the wavelength of light to be absorbedcan have a peak of relative sensitivity around a wavelength of 900 nm.In the case of performing color display, sensitivity of light of R amongR (red), G (green), and B (blue) can be made higher. Therefore, astructure where the photodiode is provided corresponding to a pixelwhich includes a display element of R can be used. By using thestructure where the photodiode is provided corresponding to a pixelwhich includes a display element of R, the number of elements includedin a pixel circuit portion and power consumption can be reduced. Thus,operating time of the mobile phone per charge can be extended.

Further, by forming the semiconductor layer included in the photodiode,which is an optical sensor, over the single crystal silicon substrate asdescribed above, the wavelength of light to be absorbed can have a peakof relative sensitivity around a wavelength of 900 nm and thesensitivity of the photodiode provided corresponding to the pixel whichincludes the display element of R can be made higher. Therefore,application to authentication utilizing blood vessels of a user ispossible. Information related to the positions of the blood vessels ofthe user is read from all or part of hands by an image sensor formed ofthe photodiode provided in each pixel. By providing a mobile phone withan authentication function, a function of increasing security ofinformation stored in the mobile phone can be added, which ispreferable.

As described in this embodiment mode, in the mobile phone of the presentinvention, the display element and the optical sensor are provided ineach of plurality of pixels. Further, as described in Embodiment Mode 1,functions used in the mobile phone, in particular, functions related todisplay and input on the display surface are switched by an arithmeticcircuit in accordance with signals from a gradient detection portion.Therefore, a mobile phone which can be used without hamperingconvinience can be provided. Further, a mobile phone which optimizes thesize or arrangement of the display portion in which optical sensors areprovided depending on functions of a mobile phone to be used and anoperating method of the mobile phone, so that operability can beimproved.

Note that this embodiment mode can be implemented in combination withany technical component in other embodiment modes in this specification.

Embodiment Mode 5

Next, with reference to FIG. 19, examples of the structures of a displaypanel which includes a pixel circuit having a display element and anoptical sensor, and a mobile phone which includes a gradient detectionportion are described.

A display panel 2001 is incorporated in a housing 2002 so as to bedetachable. The shape or size of the housing can be changed asappropriate in accordance with the size of the display panel 2001. Thehousing 2002 to which the display panel is fixed is fitted into aprinted circuit board 2003 and assembled as a module.

The display panel 2001 is connected to the printed circuit board 2003through an FPC 2004. The printed circuit board 2003 includes a speaker2005, a microphone 2006, a transmitting/receiving circuit 2007, a signalprocessing circuit 2008 which includes an arithmetic circuit, a displayportion control circuit, and the like, and a gradient detection portion2009. Such a module is combined with an operation key 2010, a battery2011, and an antenna 2012 and is stored in a housing 2013. A pixelportion of the display panel 2001 is provided so that it can be seenfrom an opening window provided for a housing 2014.

In the display panel 2001, a pixel circuit portion and part ofperipheral driver circuits (a driver circuit whose operation frequencyis low among a plurality of driver circuits) may be formed over the samesubstrate by using transistors; and part of the peripheral drivercircuits (a driver circuit whose operation frequency is high among theplurality of driver circuits) may be formed over an IC chip. Then, theIC chip may be mounted on the display panel 2001 by COG (chip on glass).Alternatively, the IC chip may be connected to a glass substrate byusing TAB (tape automated bonding) or a printed circuit board. With sucha structure, power consumption of a display device can be reduced andoperation time of the mobile phone per charge can be extended. Further,cost of the mobile phone can be reduced.

As described in this embodiment mode, in the mobile phone of the presentinvention, the display element and the optical sensor are provided ineach of plurality of pixels. Further, as described in Embodiment Mode 1,functions used in the mobile phone, in particular, functions related todisplay and input on the display surface are switched by an arithmeticcircuit in accordance with signals from a gradient detection portion.Therefore, a mobile phone which can be used without hamperingconvinience can be provided. Further, a mobile phone which optimizes thesize or arrangement of the display portion in which optical sensors areprovided depending on functions of a mobile phone to be used and anoperating method of the mobile phone, so that operability can beimproved.

Note that this embodiment mode can be implemented in combination withany technical component in other embodiment modes in this specification.

This application is based on Japanese Patent Application serial no.2007-312857 filed with Japan Patent Office on Dec. 3, 2007, the entirecontents of which are hereby incorporated by reference.

1. A mobile phone comprising: a display portion having a rectangleshape; a speaker; and a microphone, wherein the speaker and themicrophone are provided diagonally at corners of the rectangle shape ofthe display portion.
 2. The mobile phone according to claim 1, whereinthe mobile phone further comprises: a pixel circuit portion where aplurality of pixels and a plurality of transistors are arranged; anoptical sensor provided in each of the plurality of pixels; a displayelement; an optical sensor control circuit connected to an opticalsensor driver circuit which is configured to drive the optical sensorand read a signal from the optical sensor; a display portion controlcircuit connected to a display element driver circuit which isconfigured to drive the display element; a gradient detection portionwhich is configured to detect whether a gradient of the mobile phonefrom a viewpoint is in a first state, a second state, or a third state,and to output a signal in accordance with the gradient, wherein thepixel circuit portion displays images of television broadcasts in thefirst state, and displays character input keys in the second state andthe third state, and wherein the second state and the third state have alarger gradient than the first state from the viewpoint; and anarithmetic circuit which is configured to perform switching of functionsin accordance with a function used by a user related to display andinput on a display surface in accordance with the gradient.
 3. Themobile phone according to claim 2, wherein the display element is one ofa liquid crystal element, an EL element, and an electrophoretic element.4. The mobile phone according to claim 2, wherein the gradient detectionportion is one of a gyroscope and a triaxial acceleration sensor.
 5. Themobile phone according to claim 2, wherein the optical sensor is aphotodiode.
 6. A mobile phone comprising: a display portion having arectangle shape; an imaging lens; a speaker; and a microphone, whereinthe speaker and the microphone are provided diagonally at corners of therectangle shape of the display portion.
 7. The mobile phone according toclaim 6, wherein the mobile phone further comprises: a pixel circuitportion where a plurality of pixels and a plurality of transistors arearranged; an optical sensor provided in each of the plurality of pixels;a display element; an optical sensor control circuit connected to anoptical sensor driver circuit which is configured to drive the opticalsensor and read a signal from the optical sensor; a display portioncontrol circuit connected to a display element driver circuit which isconfigured to drive the display element; a gradient detection portionwhich is configured to detect whether a gradient of the mobile phonefrom a viewpoint is in a first state, a second state, or a third state,and to output a signal in accordance with the gradient, wherein thepixel circuit portion displays images of television broadcasts in thefirst state, and displays character input keys in the second state andthe third state, and wherein the second state and the third state have alarger gradient than the first state from the viewpoint; and anarithmetic circuit which is configured to perform switching of functionsin accordance with a function used by a user related to display andinput on a display surface in accordance with the gradient.
 8. Themobile phone according to claim 7, wherein the display element is one ofa liquid crystal element, an EL element, and an electrophoretic element.9. The mobile phone according to claim 7, wherein the gradient detectionportion is one of a gyroscope and a triaxial acceleration sensor. 10.The mobile phone according to claim 7, wherein the optical sensor is aphotodiode.